1. Field of the Invention
The present invention relates to an ink jet recording apparatus for recording onto a recording material by discharging ink from a recording unit.
2. Description of the Related Art
A recording apparatus can be a type having components such as an image scanner, a facsimile, a copying machine, and a printer. The recording apparatus can be a type which is used as a compound type electronic device such as computer or word-processor, or which is used as an output device such as work station. These recording apparatuses record (print) images, characters, and symbols onto a recording material (a recording medium) such as thin plastic and paper, based on recording information. For example, an ink jet recording apparatus performs recording by discharging ink from minute discharge ports of a recording head of a recording unit. If the ink jet recording apparatus is left standing for a prolonged period of time, ink viscosity can increase, dye concentration can increase, or adhesion is generated, due to evaporation of the volatile components of the ink from the discharge ports.
Moreover, a discharge failure of the ink may occur due to air bubble inclusions inside the recording head upon exchanging a detachable ink tank, or due to the bubbles clotting inside the ink flow duct of the recording head. To avoid such inconveniences due to the air bubble generation or the ink property deterioration, the discharge ports of the recording head are sealed by a cap, and then a suction unit installed inside the recording apparatus depressurizes inside the cap by using a pump to suck the air bubbles out together with the ink.
The pumps used can be a tube pump and a piston pump. The tube pump generates negative pressure which is effective inside the cap, by using a restorative force of the stroked tube by a roller. The amount of suction is changed by changing the stroking amount of the tube pump. The strength of the negative pressure is changed by changing the stroking speed of the tube pump. The piston pump generates negative pressure in the depressurized chamber connected to a cap by the stroke movement of the piston inside the cylinder. If the piston reaches the suction nozzles, the depressurized chamber is connected to the cap, and the negative pressure is induced inside the cap. The piston pump instantaneously gives a large effective negative pressure. However, in general, because the suction amount of one stroke is determined by the mechanism, in order to increase the suction amount without changing the mechanism, the strokes must be repeated.
For ink jet recording apparatuses that perform color recording or tone gradation recording, a recording head having a plurality of discharge ports (discharge orifices) that discharge various ink is used. When exchanging the ink tanks, air bubbles from the connecting unit may be introduced into the ink flow duct of the recording head. These air bubbles impede normal discharge of the ink. Upon exchanging the ink tank, a suction recovery process is performed after exchanging the ink tank, so that the air bubbles are expelled along with the ink.
Nevertheless, as for the suction recovery process of the recording head having a plurality of discharge ports as in color recording, in the case of sucking the colored ink out from the three colored ink discharge ports of cyan (C), magenta (M) and yellow (Y), these three colored ink discharge ports are capped by a single cap for performing suction, and because the ink having the worst condition among the three colored ink of cyan, magenta, and yellow had been set as the standard suction recovery condition, the following technical problems may result.
That is, the suction operation after the ink tank exchange assumes the worst condition of bubbles being incorporated in the ink flow duct, that is, the assumption is being made that the ink flow duct is totally replaced by air, so that an amount of ink which is almost equivalent to a volume of the ink flow duct is set for suction. In this case, the volume equivalent to the ink suction amount is set to an ink flow duct (for example, yellow ink flow duct) having the largest volume among the three colored ink. Because of this, the conditions of suction operation is set to a maximum amount of ink suction among the three colors, whereby the maximum amount of ink suction equals to three times the yellow ink flow duct volume (for three colors) .
Because of this, if the yellow ink tank is being exchanged, an appropriate suction amount is set. However, if the cyan or magenta ink tank is being exchanged, the suction amount is more than the necessary amount so that the ink is wasted. Because of this, a number of recording materials for recording are over-consumed. Moreover, due to the increase in the ink discharge amount, the cost of a process component for recycling and maintaining the waste ink is increased. At the same time, if a light color ink is added for the purpose of high resolution, there is going to be a further increase in the difference in each of the ink flow duct volumes with the construction of integrally capping these discharge ports, and the ink discharge amount is further increased.
Moreover, in case of sucking from a plurality of discharge ports having different diameters via the integral cap, because a discharge port of the worst condition is set as a standard suction amount, which means that a discharge port of small discharge port diameter having a large flow resistance is set as the standard suction condition. In this case also, the suction amount is appropriate if the ink tank with a small discharge port diameter is being exchanged. However, if the ink tank with a large discharge port diameter is being exchanged, the suction amount is excessive, so that the ink is wasted.
Moreover, in case of sucking from a plurality of discharge ports having different ink compositions via the integral cap, the ink having the worst condition is set as a standard suction amount, which means that the ink having the worst condition influencing the flow resistance such as ink viscous resistance is set as the standard suction condition. In this case also, the suction amount is appropriate if the ink tank with a large flow resistance (viscous resistance) is being exchanged. However, if the ink tank with a low flow resistance is being exchanged, the suction amount is excessive, so that the ink is wasted.
Likewise, in case of sucking from a plurality of discharge ports containing the dye ink discharge ports and the pigment ink discharge ports via the integral cap, the ink having the worst condition influencing the ink flow resistance such as ink viscous resistance is set as a standard suction condition. That is, the pigment ink having a high ink viscous resistance is set as the standard suction condition. Accordingly, in this case also, the suction amount is appropriate when the pigment ink tank is being exchanged. However, if the dye ink tank is being exchanged, the suction amount is excessive, and the ink is wasted.